<!DOCTYPE html>
<html lang="zh">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>显示模式-块级</title>
  <style>
    div {
      width: 100px;
      height: 100px;
      background-color: #00f;
    }
  </style>
</head>

<body>
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <ul>
    <li>独占一行</li>
    <li>宽度默认是父级的100%</li>
    <li>可设置宽高</li>
  </ul>
</body>

</html>